Wood ply construction



0d? 3 G. H. OSGOOD ET AL WOOD PLY CONSTRUCTION Filed Sept. 29, 1933UNITED STATES PATENT OFFICE WOOD PLY CONSTRUCTION George H. Osgood andRussell G. Peterson,

Tacoma, Wash.

Application September 29, 1933, Serial No. 691,568

3Claima.

This invention relates to a new article of manufacture, and moreparticularly to a veneer construction um't involving wood plies bound byan adhesive using a vegetable hemi-cellulose-containing material as abase. Our co-pending applications filed under Serial Numbers 652,692;696,544; 696,545; and 698,428 all relate to adhesives analogous to theherein-described adhesive.

v'Ihie art of making waterproof glues from various materials has beenknown for a long time; thus casein, blood albumen, vegetableproteincontaining materials and synthetic resins are in common use. Eachof these mentioned materials has some disadvantage peculiar to itself.Casein is costly and lacks uniformity; blood albumen is not available inlarge quantities and require heat for. the best results; vegetableproteins are also quite costly and only one or two species are commonlyavailable; while synthetic resins are both costly and must be appliedunder great heat and pressure. There is, accordingly, a great demand,particularly in the veneer industry, where: a large quantity of glue isconsumed, for a new glue that would be very cheap and at the same timestrong and waterproof.

By waterproof, in this connection, it is not meant that glues thuschracterized will resist the action of water indefinitely, but it ismeant that they are waterproof in the sense in which the term is used inthe veneer industry, viz., that a panel can be soaked in cold water forseventy-two to one hundred hours, or in boiling water for eight hourswithout separation.

We have now discovered that such material as the hulls and pods oflegumes, coffee bean pods, pits of dates, cottonseed hulls and othernatural sources of hemi-cellulose, when subjected to proper treatment,can be converted into a waterproof adhesive that will satisfy the rigidrequirements of veneer and plywood making. The requisite raw materialmay be derived from a number of sources at a. very low cost and thetreatment of such material is relatively simple and inexpensive and doesnot require an elaborate plant to manufacture or use, as is the casewhere hot pressing is required, so that as a result we are able toproduce a satisfactory product at a much lower cost than has heretoforebeen possible.

To accomplish the foregoing and related ends, the invention, then,consists of the combinations hereinafter fully described andparticularly pointed out in the claims, it being understood that suchconstitute but several of the ways in which the principal of theinvention may be used.

- The drawing illustrates, diagrammatically, a

portion of a panel in which an adhesive material formed by a vegetablehemicellulose, and containing an excess of caustic alkali andcarbonbisulphide, has been used, and illustrating particularly the fact thatthe adhesive penetrates into the 5 wood of the panel.

We have found that the hulls and pods of the legumes, coffee bean hulls(commonly called by producers coffee parchment), date pits, and cottonseed hulls all constitute an, admirable raw 10 material for our purpose,but we prefer to use the hulls of coffee beans and of cottonseed becauseof the sources that are available. The before mentioned materials arefirst ground to a. suitable mesh and when treated with certainchemicals, or 16 other substances, we make therefrom a very satisfactoryglue that meets the requirements of the veneer trade fully and is inmany respects better than the usual glues now on the market and muchless expensive than any of the present water-resisting adhesives. We donot, however, wish to limit ourselves to the materials hereinbeforementioned but claim the use of any natural material in which thehemi-cellulose forms the principal adhesive constituent. In the use ofa. natural material which is high in hemi-cellulose, such, as the beforementioned materials, there are no expensive separation process orpurifications necessary.

We have also discoveredthat one of the rea- 30 sons for the secure bondbetween the wood plies in a panel in which our glue is used is onaccount of the softening effect of the wood fibres along the surfaces ofthe wood exposed at the glue line, by the considerable excess of causticalkali and 35 carbon bisulphide contained in the glue. This softeningpermits a better penetration of the glue into the cells of the wood andtherefore produces a stronger adhesion than would be possible withoutthis softening effect. Further, the acid con- 40 tent of the wood, suchas tannic acid, acetic acid, etc., commonlypresent in timber gives anatural acid treatment to the partially viscosized wood' fibres adjacentto the glue line and also to the hemi-cellulose viscose used as abinder. This 45 acid treatment by the natural acids in the wood rendersthe glue bond practically insoluble in water. The addition of acids toviscose is a wellknown method of regenerating cellulose, while thisnatural acid method gives practically the 50 same effect without theaddition of chemicals.

The vegetable hemi-cellulose-containing material is first ground to 8 or10 mesh and'is steeped in a 16 to 24 percent caustic solution for one ortwo hours, then this mass is submitted to a pressure of about two-tofour-hundred pounds per square inch. The pressure applied would dependon the amount of material being pressed, the larger amounts requiringthe higher pressure. This leaves about 150% to 200% (of the originalweight of the meal) of caustic solution in the material. The glue baseis thus kept in this condition until it is required for use. The mass isthen treated with carbon bisulphide, in the amount of about 25% of theoriginal weight of the dry meal used, for about four hours, and is thendiluted with about 150% (dry meal) of water and 20% caustic soda. Othermaterials may be added to decrease the time required for the glue toset.

The particular order in which the several ingredients are mixed togetherin the formula may be varied, and it is not necessary that themanufacture of the adhesive be completed in a continuous singleoperation, but, as a matter of practice, we have found it desirable incertain cases to mix only certain of the ingredients initially and thenadd others just before the glue is required for use.

After the glue is ready for use, it is then spread on the plies of woodor veneer by suitable means, and the plies of glued and unglued veneersassembled as is customary in a veneer or plywood factory, and thenpressure is applied by suitable means, and this pressure is retained forsix or more hours by either leaving the stack of glued panels in thepress or by means of retaining clamps.

Other modes of applying the principle of our invention may be employedinstead of the one above explained, change being made in regard to theprocess herein disclosed or the materials employed in carrying out suchprocess provided the stated ingredients and steps are the equivalents ofthe stated ingredients or steps we employ.

Having, therefore, described our invention, what I we claim and desireto secure by Letters Patent,

1.- As an article of manufacture, a veneer construction unit comprisinga plurality of wood plies bound together by a vegetablehemi-cellulosecontaining adhesive which contains a sufllcient excess ofcaustic alkali and carbon bisulphide to soften the wood fibres along theglue line whereby the natural acids of the wood react on the cellulosicmaterials to form a waterproof bond.

2. In a laminated construction unit, wood in plural layer form boundresistantly against water separation by the reaction products of thenatural acids in the wood with composition which includes a vegetablehemiellulose-containing material as its. principal adhesive ingredienttogether with an excess of caustic alkali and carbon bisulphide, wherebysaid excess of caustic alkali softens the wood fibres adjacent the glueline and said carbon bisulphide partially viscosizes the said softenedwood fibres, and whereby the hemi-cellulose and said partiallyviscosized fibres are acted on by the natural acids in the wood toneutralize the excess caustic alkali and thereby to increase the 'waterresistance of the glue line, and to regenerate the cellulose of thefibres. 2,5

3. As an article of manufacture, a veneer construction comprising aplurality of wood plies bound together by an adhesive which includes thereaction products of the natural acids in the wood with a vegetablematerial whose principal adhesive ingredient is hemi-cellulose togetherwith an excess of caustic alkali and carbon bisulphide, said excess ofcaustic alkali being adapted to soften the wood fibres adjacent the glueline and said carbon bisulphide being adapted to partially viscosize thesaid softened wood fibres, and the natural acids in the wood beingadapted to neutralize the excess caustic alkali to increase the waterresistance of the glue line and to regenerate the cellulose oi' thefibres.

GEORGE H. OSGOOD. RUSSELL G. PETERSON.

